Acute hepatic failure (AHF) with Stage 4 coma is a serious illness with over 60% mortality when treated with supportive therapy. The BioLogic-DT is an extracorporeal liver support device in which blood passes through cellulosic packages with a suspension of powdered charcoal and cation exchanger sorbents on the opposite side. This device effectively removes many organic toxins of 100-300 m.w. including aromatic amino acids, but removes only small amounts of ammonia. It does not increase branch chain amino concentrations in blood. Nonetheless, over 80% of liver failure patients improve physiologically and neurologically during treatment with the device; most recover liver function or proceed to liver transplant. In the current study, we will add acid-filled liquid membrane capsules to the sorbent suspension to remove ammonia, and will pre-load the charcoal with branch chain amino acids to return these amino acids to the patient during treatment. In vitro tests will determine.the effect of these sorbent changes on ammonia removal and branch-chain generation, and will determine whether there is any loss of organic toxin removal. Phase II clinical studies will determine whether the new chemical functions of the sorbent improve the treatment of patients with hepatic coma.